KUALA LUMPUR (Reuters) - A sacked Malaysian deputy prime minister and critic of scandal-tainted Prime Minister Najib Razak registered a political party on Tuesday saying he wanted to offer ruling party members an alternative and to fight corruption.

The former minister, Muhyiddin Yassin, along with former premier Mahathir Mohamad, have been leading a campaign to unseat Najib after he was linked to a multi-billion dollar graft scandal at state fund 1Malaysia Development Berhad (1MDB).

Najib has denied any wrongdoing and consolidated power within the ruling United Malays National Organisation (UMNO) party. The prime minister has also cracked down on dissent.

“As a former UMNO member, I know there are many who are unsatisfied about the current leadership, but they’re not ready to say it out loud,” Muhyiddin said after submitting registration documents in Putrajaya, Malaysia’s administrative capital.

“So now, there is a new space for them.”

UMNO has ruled Malaysia largely unchallenged since independence in 1957, with the support of the majority ethnic Malay community, though it fared poorly, losing the popular vote, in the last election in 2013.

Muhyiddin is expected to lead Parti Pribumi Bersatu Malaysia (Bersatu), or United Malaysian People’s Party, as its president, while Mahathir will serve as party chairman, an aide to Muhyiddin said.

Mahathir, Malaysia’s longest-serving prime minister, had announced plans for the new party in July, after months of attacks against Najib’s leadership and alleged graft and mismanagement at 1MDB.

The United States Department of Justice filed lawsuits last month to seize more than $1 billion in assets linked to 1MDB.

The Wall Street Journal has reported that more than $1 billion was diverted from 1MDB to Najib’s personal bank accounts.

“We want to strengthen efforts in the fight against corruption and abuse of power, as well as uphold social justice and fair distribution of wealth,” Muhyiddin said.

But political commentators have said the new party will likely have little impact as top UMNO members stand behind Najib.

Muhyiddin was sacked as deputy prime minister in July 2015, after criticizing Najib’s handling of the 1MDB scandal.

Nearly a year later, Najib announced an UMNO supreme council decision to expel Muhyiddin, along with Mahathir’s son, Mukhriz Mahathir, from the party.

Mahathir quit UMNO in February, saying it was seen as “supporting corruption” under Najib’s leadership.

Mahathir, 91, was hospitalized for treatment of a chest infection on Tuesday. The veteran politician, who was prime minister for 22 years until 2003, will be under observation for the next few days, an aide said.